# -*- coding: utf-8 -*-

import sys
import os
import math


x1, y1, x2, y2 = list(map(float, input().split()))
x_diff = x1 - x2
y_diff = y1 - y2
d = math.sqrt(x_diff ** 2 + y_diff ** 2)
print(d) import sys sys import os os import math math x1, y1, x2, y2 = list(map(float, input().split())) x1 list(map(float, input().split())) list map(float, input().split()) map float input().split() ().split () input split y1 x2 y2 x_diff = x1 - x2 x_diff x1 - x2 x1 x2 y_diff = y1 - y2 y_diff y1 - y2 y1 y2 d = math.sqrt(x_diff ** 2 + y_diff ** 2) d math.sqrt(x_diff ** 2 + y_diff ** 2) math.sqrt math sqrt x_diff ** 2 + y_diff ** 2 x_diff ** 2 x_diff 2 y_diff ** 2 y_diff 2 print(d) print d x2, y2 = list(map(float, input().split())) list(map(float, input().split())) x2 d = math.sqrt(x_diff ** 2 + y_diff ** 2) math.sqrt(x_diff ** 2 + y_diff ** 2) d y2 = list(map(float, input().split())) list(map(float, input().split())) y2 y1, x2, y2 = list(map(float, input().split())) list(map(float, input().split())) y1 y_diff = y1 - y2 y1 - y2 y_diff x1, y1, x2, y2 = list(map(float, input().split())) list(map(float, input().split())) x1 x_diff = x1 - x2 x1 - x2 x_diff
# -*- coding: utf-8 -*-

import sys
import os
import math


x1, y1, x2, y2 = list(map(float, input().split()))
x_diff = x1 - x2
y_diff = y1 - y2
d = math.sqrt(x_diff ** 2 + y_diff ** 2)
print(d)